Micro-Electro-Mechanical Systems (MEMS) for drug delivery applications have attracted significant interest leading to extensive investigation. Implantable MEMS devices for drug delivery are designed for controlled release of drugs locally at diseased sites through miniaturized devices. Site-specific drug delivery offers more effective therapies for non-systemic diseases or disorders as compared with conventional methods using systemic drug administration that can cause negative impacts on non-diseased areas of the body.
For implantable devices, the elimination of a wired interface is advantageous. Implantable devices with active circuitry require batteries or other power supplies that must be recharged or replaced for continued operation. Passive implantable devices do not require batteries, but suffer from implementation issues including small actuation force and stroke, use of high voltages, micromachining and integration of ferromagnetic materials, and actuator/system packaging. For example, one type of passive device uses electrostatic force to drive an actuator and usually requires high voltages which are generated wirelessly.
Some systems rely on thermal actuation induced by energy-beam-assisted heating. These systems tend to be complicated and large. In cases where the target actuator makes a movement, for example in micro-robotic applications, the beam control system needs to include an automated function that precisely directs the beam to the moving target to ensure continuous actuation. These difficulties increase further when multiple actuators are involved. Moreover, thermal actuation induced by energy-beam-assisted heating is ineffective when there is an object obstructing the beam path; thus, energy-beam-assisted heating cannot be used to actuate devices implanted inside the body.